16 



BIRDS IN THEIR RELATIONS TO MAN. 



be marked either on the leg or on the side of the bill with a 

 nitrate of silver pencil, which may be purchased at any drug 

 store. There may be some difficulty in applying the pencil so 

 as to make a good mark, owing to the oily skin of the birds, 

 but see that it is wet and keep rubbing. The marks will 

 need to be renewed occasionally. 



The great value of this method is that it enables one to 

 get photographs of the birds as they "are being fed, beautiful 

 examples of which are shown in Professor Herrick's book. 

 There are, however, elements of danger to the birds, which 

 should by no means be overlooked. There is danger of 

 desertion by the parents, of too much exposure to the hot 

 rays of the sun, of lack of protection from the cold of night 

 or of the storm and stress of weather, as well as of various 

 living enemies. No one should remove a nest from its original 

 site who is not willing to take every possible precaution to 

 avoid a tragedy. 



HEAD OF BROWN THRASHER. 



